You've gotten some answers below, but one answer is: There are several common ways of handling this, from powerline communication to cellular to LPWAN approache

You've gotten some answers below, but one answer is: There are several common ways of handling this, from powerline communication to cellular to LPWAN approaches, and all of them are in use, with different trade-offs. There's no one standard for smart metering infrastructure. Older AMR approaches often would just broadcast a signal that you could pick up with a vehicle driving around the neighborhood, but they're one way only. AMI uses cell, PLC, LPWAN, and sometimes zigbee (to a neighborhood gateway). What your meter uses depends on your power company and when it was installed.